1. Field of the Invention
The present invention relates to a testing apparatus for magnetic recording media, testing method for magnetic recording media, and production method for magnetic recording media including the testing method which are suited for use in defect testing as well as certify testing such as bit error rate testing, and parametric (electromagnetic conversion properties) testing pertaining to magnetic recording media used in hard disk drives and the like.
Priority is claimed on Japanese Patent Application No. 2007-24511, filed Feb. 2, 2007, the content of which is incorporated herein by reference.
2. Description of the Related Art
Magnetic recording devices typified by hard disk drives are widely used as external memory units of information processing devices such as computers, and in recent years have also come to be used as video recording devices for animated images.
Hard disk drives ordinarily include: a shaft wherein a discoid (donut-shaped) magnetic recording medium with an opening at the center is rotated alone or concentrically in a superimposed plurality (synchronous rotation is conducted in the case of a plurality); a motor which is joined via bearings to the pertinent shaft and which causes rotation of the magnetic recording medium; magnetic heads used for recording and/or playback on both faces of the magnetic recording medium; multiple support arms to which the pertinent heads are attached; and a head stack assembly which is capable of synchronously moving said multiple support arms, and which causes the magnetic heads to move to desired positions on the magnetic recording medium. Furthermore, the magnetic heads used for magnetic recording playback are ordinarily floating-type heads, and move at a fixed floating height on the magnetic recording medium.
Recording regions, which are called “tracks” in the radial direction and “sectors” in the circumferential direction, are formed on the magnetic recording medium. Reading and writing of information on the magnetic recording medium are conducted in track and sector units. A controlling magnetized pattern that serves to control the magnetic heads is formed on each track. The signals obtained from this controlling magnetized pattern are called servo signals. In the case where the intervals between information recording tracks of the magnetic recording medium are narrowed to increase the number of tracks, the servo signals are also correspondingly provided in a dense—that is, more numerous—manner in the radial direction of the disk, and it becomes necessary to enable conduct of precise control of the magnetic heads.
Magnetic recording media loaded into hard disk drives are manufactured by the following process. After conducting texturing treatment and the like on the surfaces of a substrate generally composed of aluminum alloy or glass or the like, the magnetic recording medium is prepared by sequentially forming a base layer, magnetic layer, protective layer, lubricating layer, etc. Subsequently, glide testing and certify testing are sequentially conducted on the obtained magnetic recording medium.
Glide testing is testing of whether or not protrusions exist on the surface of a magnetic recording medium. That is, when a magnetic recording medium undergoes recording playback with use of magnetic heads, if there exist protrusions with a height equal to or greater than the floating height (the interval between the medium and the magnetic head) on the surface of the magnetic recording medium, these will cause damage to magnetic heads as the magnetic heads strike the protrusions, and defects in the magnetic recording medium. In glide testing, a test is conducted as to whether or not protrusions of such height exist (e.g., see Patent Document 1, i.e. Japanese Unexamined Patent Application, First Publication No. H10-105908).
Certify testing is conducted on magnetic recording media which pass glide testing. In a manner similar to the recording and playback of an ordinary hard disk drive, certify testing records prescribed signals on a magnetic recording medium with a magnetic head, after which the signals are played back. The quality of the medium—e.g., electrical properties and existence or absence of defects pertaining to the magnetic recording medium—is then ascertained be detecting recording inabilities of the magnetic recording medium from the obtained playback signals (e.g., see Patent Document 2, i.e. Japanese Unexamined Patent Application, First Publication No. 2003-257016). Accordingly, certify testing confirms the ability to play back prescribed signals by magnetic head in a manner similar to the recording playback of a hard disk drive. Consequently, it is preferable prior to certify testing to conduct a test which detects recording inabilities of the magnetic recording medium by writing servo information signals into the magnetic recording medium using a device called a “servowriter” in a manner similar to the method of use of an actual hard disk drive.
However, to write servo signals into a magnetic recording medium generally requires 30 minutes to 2 hours of time per disk, depending also on the size of the magnetic recording medium. Accordingly, writing servo signals into magnetic recording media prior to certify testing causes a reduction in productivity with respect to magnetic recording media. Furthermore, due to the recent increase in demand for magnetic recording media, there is a need for certify testing apparatus capable of testing numerous magnetic recording media in a shorter time.
At the same time, the recording density of magnetic recording media has grown ever higher in recent years, and there is a need to conduct high-precision certify testing using test methods which are closer to the actual method of use of magnetic recording media in hard disk drives.
The present invention has been made in light of the aforementioned problems, and its object is to provide a testing apparatus for magnetic recording media and a testing method for magnetic recording media which enable the conduct of high-precision certify testing close to the actual method of use of magnetic recording media in hard disk drives in a short time.